1. Field
An aspect of the present invention relates to a semiconductor device, and more particularly, to a field effect power electronic device.
2. Description of the Related Art
The development of various forms of wireless communication technologies and semiconductor technologies has remarkably changed modern society and has provided various conveniences. This technology development started with the development of semiconductor devices in the early 20th century. All current electronic products and communication products include various electronic devices.
In order to put such electronic products and communication products as final products in the market, reliability of the products should be measured. The reliability of the measured products should satisfy a certain level of standard such that the products have commercial values. The reliability indicates possibility that a test sample will perform required functions for a given period of time under a given condition. Here, the sample may include a single item, a component, a device, a subsystem, a function unit, equipment, or a system.
An electronic device, particularly a high-power electronic device which produces a high output may be frequently used in a power amplifier. The power amplifier may be not only a most important component in a communication system but also a component having the highest price. Accordingly, many researches on characteristics and reliability of the power electronic device constituting the power amplifier have recently conducted and attracted great interest from developers. In addition, the power electronic device also forms the largest commercial market. The power amplifier has come into the spotlight as the most important core device not only in wireless communication such as fourth generation long term evolution (LTE) communication in recent years and fifth generation communication in future but also in military components such as radar.
The power electronic device is an electronic device which is applied to the power amplifier and produces the highest output at a transmitting/receiving terminal. Particularly, characteristic indexes representing characteristics of the power electronic device are output power, output gain, P1dB, efficiency, and the like. Among these characteristic indexes, the output power may be used as a reference for classifying power electronic devices. That is, the output power may be defined as power that a power electronic device can output as the power of the power electronic device is saturated. In order to increase the output power, the structure of a device may be defined by connecting a plurality of power electronic devices in parallel. However, due to a limit of real power electronic devices, there is a limitation in increase of output power even though a plurality of power electronic devices are connected, thereby resulting in a rapid decrease in power gain. Therefore, the size of the power electronic device cannot continuously increase.
Generally, a field effect power electronic device may be frequently used as the power electronic device. The field effect power electronic device may include a source, a drain, and a gate, and has characteristics of high output and high frequency. Thus, the field effect power electronic device is most frequently used as a radio frequency (RF) power electronic device. Here, the source of the field effect power electronic device may be grounded, and the gate and the drain may operate as an input terminal and an output terminal, respectively. The characteristics of the field effect power electronic device may be influenced by an epilayer constituting the device or a unit value of the structure of the device. Particularly, RF characteristics of the field effect power electronic device may influenced by a distance between the source and the gate or a distance between the gate and the drain. Therefore, in order to achieve optimal characteristics of the field effect power electronic device, an optimal structure of the device should be determined through many researches.
In order to produce sufficient output power, the power consumed in a power electronic device may be influenced by efficiency. When a real power electronic device operates, the percentage of output power to DC power applied to the device may be defined as efficiency. Here, most DC power that does not output as the output power is transformed into heat to be diffused to the outside of the power electronic device.
Since much heat may be generated inside the power electronic device, the reliability and durability of the power electronic device may be determined according to how much heat is diffused from the inside to the outside of the power electronic device. Particularly, in the case of the field effect power electronic device, heat generated inside the device increases temperature, which may have influence on the mobility of carriers. That is, if the temperature of the field effect power electronic device having high-frequency characteristics increases, the speed of the carriers decreases, and therefore, the high-frequency characteristics may be deteriorated corresponding to the increase in temperature.
As described above, in the power electronic device, the internal temperature and the diffusion of the heat from the inside to the outside are very important in the reliability and durability of the power electronic device, and many researches for solving such a problem have recently been conducted.
Particularly, when the field effect power electronic device operates as the movement of carriers is performed in a channel layer, the temperature in the channel layer may be highest.
The size of the field effect power electronic device may be defined as the width of the entire gate. Thus, the field effect power electronic device can generate high output power by increasing its size, i.e., the width of the gate. However, as the size of the field effect power electronic device, i.e., the width of the gate increases, heat generated inside the field effect power electronic device is not easily diffused to the outside. Hence, the internal temperature of the field effect power electronic device may further increase.
The field effect power electronic device may be fabricated as a multi-gate type field effect power electronic device having a plurality of gates. In the multi-gate type field effect power electronic device, heats generated from the gates have influence on each other, which may not only further increase the temperature of the field effect power electronic device but also generate hot spots. Particularly, the hot spot generated inside the field effect power electronic device rapidly deteriorates characteristics of the field effect power electronic device. As a result, the field effect power electronic device may be broken.
Accordingly, the problem that heat is generated inside the field effect power electronic device should be solved so as to improve the reliability and durability of the field effect power electronic device.